TrisomyDown SyndromeChromosomes, Human, Pair 18Chromosomes, Human, Pair 13Chromosome DisordersKaryotypingChromosomes, Human, Pair 21Nondisjunction, GeneticChromosomes, Human, 16-18Nuchal Translucency MeasurementPrenatal DiagnosisAneuploidyMosaicismMaternal AgeChorionic Gonadotropin, beta Subunit, HumanChromosome AberrationsPregnancy-Associated Plasma Protein-AChromosomes, Human, 13-15Fetal DiseasesSex Chromosome DisordersPregnancyPregnancy Trimester, FirstTurner SyndromeAbnormalities, MultipleUltrasonography, PrenatalAbortion, SpontaneousIn Situ Hybridization, FluorescenceSex Chromosome AberrationsTranslocation, GeneticTrophoblastic Tumor, Placental SiteChromosome BandingNeckCytogenetic AnalysisChromosomes, Human, 6-12 and XDiploidyGestational AgeHeart Rate, FetalPregnancy Trimester, SecondFetusNasal BoneChromosomes, Human, 21-22 and YChromosomes, HumanFetal DeathFalse Positive ReactionsChromosomes, Human, Pair 15DermatoglyphicsPregnancy, High-RiskMeiosisAmniocentesisCrown-Rump LengthChromosomes, Human, Pair 8MonosomyChromosomes, Human, Pair 12Chromosomes, Human, 19-20Chorionic Villi SamplingChromosomes, Human, 4-5Chromosomes, Human, Pair 7Sensitivity and SpecificityChromosome Mapping